1. Field of the Invention
The present invention relates in general to a driving integrated-circuit (IC). In particular, the present invention relates to a differential signal circuit and a driving circuit of a liquid crystal display (LCD) comprising driving ICs connected in serial.
2. Description of the Related Art
FIG. 1 shows the conventional data-bus transmitting signal by differential-type signal. The processor 10 outputs differential signals to the driving ICs 14A˜14C through data-bus 12. Here, the differential signals are transmitted when the input impedance and the output impedance of both sides of the data-bus match. Thus, terminal resistor 16 is utilized for obtaining impedance matching between the data-bus 12 and the processor 10.
Each driving IC is respectively connected to the data-bus 12 in parallel to receive the differential signals output from the data-bus 12. The processor 10 is the timing controller when used in a liquid crystal display (LCD). The differential signals are transformed to data signals after being received by the driving ICs 14A˜14C, and the data signals are output to the data electrode driver of the LCD to drive the data electrode according to the synchronized pulses output from the data-bus 12.
FIG. 2 shows a circuit of the conventional driving IC 20. The data receiving circuit 22 transforms the data of the data-bus 12 to digital signals and outputs to the digital-analog converting circuits DAC1˜DAC384. The digital-analog converters DAC1˜DAC384 convert the digital signals to analog signals S1˜S384, then transmit the analog signals S1˜S384 to data electrode driver 24 to drive the data electrodes of the LCD 26. Here, the driving IC 20 comprising 384 channels is used as an example. The driving IC 20, however, may comprise 402, 420, or 480 channels.
The data transmitted to the driving IC from the data-bus 12, however, is video data, thus, the layout is complicated. For example, the layout of the nodes 18A˜18C of the driving ICs 14A˜14C and the data-bus 12 is very complicated. Thus, more layout space and potentially even more layers of IC board are required. Thus, the cost and the complication of layout increase.
In addition, the mass data lines between the driving ICs 14A˜14C and the data-bus 12 complicate the layout trace, causing electromagnetic interference.